I cleaned up a antique rifle a few years back that turned out good but I can"t remember what I used. I"m thinking Krud Kutter or something of that nature may work. I"m sure you will get a lot of good answers here.
I'd also suggest Natchez Solution. I use it on all my wood-stocked rifles and it really works well on any worn finishes as well as the new finish found on Marlins and Rugers too. It especially does wonders on the lightly finished areas of checkering found on many new rifles.
A light wiping on wood and metal with Snake Oil will really make a difference in the whole gun. I keep my Snake Oil rag in a zip lock bag, and wipe all my guns down with it. Add a few drops once in awhile to keep the rag working.